1. Field of the Invention
Aspects of the present invention relate to a cylindrical secondary battery, and more particularly, to a cylindrical secondary battery that can prevent an increase of internal resistance, by preventing the movement of an electrode assembly.
2. Description of the Related Art
Generally, a cylindrical secondary battery includes a cylindrical electrode assembly, a cylindrical can to house the electrode assembly and an electrolyte, and a cap assembly to seal an upper opening of the can, and to allow current generated in the electrode assembly to flow to the outside.
The electrode assembly is formed by arranging a separator between a cathode plate and an anode plate, and winding the same into a jellyroll-type shape. A cylindrical center pin is inserted into the middle of the electrode assembly. In other words, the center pin is inserted into a space that is formed by removing a shaft that is used to wind the electrode assembly. The center pin prevents deformations of the electrode assembly, and discharges gas generated in the battery, to an upper part of the battery. In addition, upper and lower insulation plates are provided at upper and lower parts of the electrode assembly. The upper and lower insulation plates prevent a short between the electrode assembly and the cap assembly, or between the electrode assembly and the cylindrical can.
The electrode assembly is received in the cylindrical can, and then a beading part is formed on an upper portion of the can, to prevent the electrode assembly from moving in the can. In addition, a gasket is provided inside the upper opening of the can, to secure various battery components, and to seal the can. The cap assembly is disposed inside the gasket, to finish the upper opening of the can. Then, the can is crimped at the upper opening, to combine a cap-up of the cap assembly with the gasket. Finally, the battery is covered with an outer case, thereby completing the cylindrical secondary battery.
The manufacturing cost of each component may be increased, as the gasket, the center pin, and the insulation plate are formed in independent processes. Accordingly, the entire manufacturing process of the cylindrical secondary battery becomes complicated, and manufacturing time is increased. When an impact, such as a drop, is applied to the battery, the center pin may be separated from the electrode assembly, and may damage the cap assembly. In addition, when the cylindrical secondary battery is used as a power supply of an electric tool, the internal electrode assembly may be severely vibrated, by vibrations of the electric tool. The vibrations may increase the internal resistance (IR) of the battery, and cause problems, such as fires and explosions.